This invention comprises a short motion swim fin that functions as a stretching device to stretch and increase the arch of the foot, and as a training device to strengthen the leg muscles that are used with the motions of flutter kick. This invention differs in design, function, and mechanics from the prior art relating to swim fins, wherein it is an improved training device for the competitive swimmer; and not designed or intended as a more efficient propulsion device. This invention is a training swim fin that when used over time will improve a swimmer""s performance for competitive swimming without fins.
This invention is intended and designed specifically for use with the flutter kick, which is a short, fast motion kick, used for the front or back crawl whereby the body is parallel to the surface of the water with the legs moving up and down from the hips, in short, fast motions, knees slightly bending, and the feet kept loose. The extent of flexible arching of the feet is the critical element for converting the leg motion into propulsion by presenting an angle of attack from the loosely arching foot on every downward kick. The downward kick is the power portion of the flutter kick, whereas the upward motion is more for balance and recovery. In the back crawl, the downward kick and upward motion reverse functions. The loosely arching function acts, if you will, as a propeller blade. In fact, many swimmers have a flutter kick that defines a spiral wake as a result of a well-defined arch. Although applicant""s invention produces an impressive increase in propulsion, it does so as a result of short, fast, kicking motions, and accordingly is not designed or intended to conserve energy.
Whereas the relevant art studied discloses swim fins that are, for the most part, designed to function for underwater diving, and as such function for the propulsion efficiency in order to conserve energy. They do so by using a common principle whereby the fin, in one form or another, is worn as a flexible extension of the foot so that the fin itself presents a greater surface, and angle of attack against the water. This principle is well suited where conservation of energy, or air supply, is the primary consideration; but these fins are larger and also require a slower, longer kicking motion, comparable to using a larger gear to transfer power to a smaller gear for speed. These larger fins are not practical for the short, fast kicking motions of the flutter kick, or more specifically, as a training device for competitive swimming without fins.
In addition to the originality in use of this invention, there is also uniqueness in the design and mechanics. Specifically, it is a short tapered fin, that when worn on the forward portion of the foot, acts as a lever to the foot with the fulcrum of that lever being on the underside of the foot. The effect of this lever action stretches the arch of the foot on every downward kick. The rigidity of the fin is also adjustable to the particular swimmer by varying the taper of the fin.
The vast majority of the prior art patents cannot be practically used, or is not disclosed to be used, in a similar way as applicant""s invention, specifically, as a stretching and training fin for the competitive swimmer and in particular, for the short motions of the flutter kick used in competitive swimming except for applicant""s U.S. Pat. No. 6,123,594 and pending application Ser. No. 09/606,361, filed Jun. 29, 2000. Generally the prior art does not employ the same mechanics, or make any similar claims of the mechanics for a swim fin with a tapered flexible body to lever the arch of the foot.
The following prior art have as a common objective to be used in a dynamic fashion for moving a swimmer through the water more efficiently. This is shown in U.S. Pat. Nos. 5,597,336; 5,552,748; 3,789,448; 2,556,894 which are generally considered relevant to the disclosure.
U.S. Pat. No. 5,597,336 to Evans, has an open instep, with planar heel, so as to accommodate a plurality of foot sizes and discloses simplification of a single, two part, molding process. It is designed as a propulsion enhancement device with an elongated, flexible blade that has stiffening ribs under the foot, along the longitudinal axis of the fin, and also features unique protuberances to further reduce drag upon the blade surface.
U.S. Pat. No. 5,552,748 to Cressi discloses a three-part swim fin that has all the parts joined along the bottom of the shoe, which is a full shoe attached to a forked, arcuate part that holds the elongated fin. This arrangement is primarily intended to reduce the costs of production as compared to that of molded rubber fins. A flipper for enhancing propulsion is provided, wherein the fin has an elongated, flexible, obtuse angle to the shoe, or bottom of the foot.
U.S. Pat. No. 3,789,448 to Mitchell discloses a swimming aid for hand and foot propulsion that works on foot propulsion by using the legs in a pedaling, or climbing motion, whereby its design cause a stronger push against the water on the backward motion that it does on the forward motion.
U.S. Pat. No. 2,556,894 to Axiotes, discloses a swimming device for hand and foot propulsion that works on foot propulsion by using the legs in a pedaling, or climbing motion, whereby the device is kept in a perpendicular attitude to the leg on the backward motion to push against the water, and straightened, or feathered, on the forward motion for less resistance.
Applicant""s U.S. Pat. No. 6,123,594 is directed to the field of this invention but this application represents a distinct improvement thereover and is far more economical to produce with fewer parts and facilitates insertion of the foot and accommodates various shoe sizes. The remaining U.S. Patents are mentioned as being merely of interest: U.S. Pat. Nos. 5,683,279; 3,302,223, 1,674,807; 3,922,740. U.S. Pat. No. 5,583,729 to Raasch, et al, provides a multi-part diving fin designed for propulsion enhancement with a pivotal footplate that engages the blade, or fin portion, in a manner that allows for adjusting the tension of the elongated blade according to the swimmer""s ability.
U.S. Pat. No. 3,302,233 to Ciccotelli, discloses a swim fin comprising a rigid, flat sole plate that hinges a U-shape element, holding a flexible web, as the fin portion. The swimming motion of the leg causes the frame to move up and down independently from the motion or position of the boot, in a manner that is tensioned cantilever, so arranged as to present a greater angle of attack to the water on the downward motion than on the upward motion. The swim fin is designed to enhance propulsion with minimal strain on the foot.
U.S. Pat. No. 1,674,801 to Schwalge, discloses a swimming appliance that is used with a pedaling or climbing motion whereby the pushing direction offers more resistance to the water than the pulling direction resulting in horizontal or vertical propulsion. This swimming appliance also features a reinforced sole that is suitable for limited walking out of the water.
U.S. Pat. No. 3,922,740 to Potter is a hand paddle and not applicable for wearing on the foot.
This invention relates to swim fins and particularly to short motion swim fins. The rigid U-shape frame of U.S. Pat. No. 6,123,594 is replaced by a flat plate of thin, flexible material such as spring steel or a fiberglass composite in the parent case Ser. No. 09/606,361, filed Jun. 29, 2000. In the aforementioned application, the width end that fits under the arch of the foot is still referred to as the base end in the pending application. The plate is kept flexible on the length; but made rigid on the width by fastening non-flexible ribs running along the width on the bottom side of the plate. These ribs, or stiffeners, are fabricated from aluminum or a rigid composite material. The ribs are fastened to the plate by rivets or by lamination in the configuration described so that the plate remains flexible along it""s length, but made to be rigid along it""s width. The plate with attached stiffeners, is enclosed by the inner rubber sleeve in the same manner as the U-frame design whereby it forms a double surfaced closure on one end, but on the other end has only one diagonal flap that is folded over the base portion of the plate and secured so that it provides a rubber cushion to the bottom of the foot against the hard base edge of the plate.
The present invention, however, comprises a single molded piece of composite rubber that has a tapered thickness and a tapered shape. An outer sleeve secures the foot in place on the fin and rear bindings are used to connect the fin to the rear of the foot. The fin has a narrowed inner width that results in sleeve looseness along the edge for easier foot insertion. The tapered thickness improves the performance of the fin by producing a faster flexing action at the sculling edge and increases the overall strength by a more even distribution of flexing stresses. The invention eliminates a number of parts used in the prior art designs and is considerably less expensive.
Because the rigid U-shaped frame of applicant""s U.S. Pat. No. 6,123,594 does not bend or flex it acts as an efficient stretching device when used with the flutter kick. Only the flexibility of the rubber sleeves dampens the forces placed upon the foot and leg muscles. Because of the limited flexibility of the rubber sleeves, the stress on the arch of the foot and leg muscles is considerable and can cause muscle cramping, particularly with swimmer""s who have very muscular legs and/or a limited range of ankle motion.
On the other hand, the flexibility of the tapered design in this invention places less stress on the foot and, in fact, the stress can be controlled by the thickness of the material and the degree of taper or by varying the hardness of the material. In effect, the tapered fin design allows for different stress levels according to the swimmer""s choice and/or ability.
Accordingly, an object of this invention is to provide effective training swim fins for the competitive swimmer to use in swimming workouts to improve upon the propulsion efficiency of his or her flutter kick in competition, or when not using swim fins.
A more specific object of this invention is to provide substantially rigid, short motion, swim fins that are worn on the forward portion of the feet, so as to arch the entire foot including all joints distal to the ankle.
Another specific object of this invention is to provide swim fins of a calculated small size, with a tapered body and width that is flexible on the length but substantially rigid on the width to function as a lever to stretch the arch of the foot, so that the foot itself is included in the angle of attack. So in effect, the mechanics of the invention causes the foot to flex by the force of the water against the fin with every downward motion of the flutter kick.
A further object of this invention is to provide longitudinally flexible, short motion swim fins, that are small enough to allow a fast motion, but in a manner that requires the flexing motions of the entire foot, and as such also involves and strengthens those corresponding fast twitch leg muscles.
A still further object of this invention is to provide a pair of swim fins that are both the same and therefore interchangeable on either foot, and with one size to fit most foot sizes.
A still further object of this invention is to provide attachment components that with the tapered design make insertion of the foot of the swimmer relatively easy.
A more specific object of this invention is to provide an economical molded new and improved tapered swim fin with an interior narrowed width and which is tapered lengthwise and thickness wise.